A woman takes photos of the scene of a shooting outside the Empire State Building on Fifth Avenue August 24, 2012 in New York City. Mario Tama/Getty Images/AFP

HACKENSACK, N.J. — On Friday morning, Jeffrey Johnson, who lost his job as a clothing designer a year ago, shot and killed Steven Ercolino, the vice president of the women's apparel company where Johnson had worked, near the Empire State Building.

Johnson and Ercolino had exchanged accusations of harassment when Johnson worked at Hazan Imports, according to New York City Police Commissioner Raymond Kelly. Police said Johnson blamed the victim for his dismissal, believing Ercolino had failed to promote Johnson's line of women's T-shirts.

Friday's events have placed a spotlight on homicides in the workplace. Yet government data show such crimes are down dramatically.

From 2004 to 2008, an average of 564 work-related homicides occurred annually in the United States. In 2010, the most recent year available, there were 518, down more than 50 percent since peaking in 1994, according to the federal Bureau of Labor Statistics.

This is a trend that is surprising given the economic burden facing millions during and since the Great Recession, said Dr. Ronald Schouten, director of Law and Psychiatry Services at Massachusetts General Hospital in Boston.

"In spite of the terrible economic conditions we've had, they just do not seem to have given rise to the increase of workplace homicides in general and those perpetuated by current or former co-workers," said Schouten, also an associate professor of psychiatry at Harvard Medical School. Schouten added that the trend follows the overall decrease in violent crime nationwide.

Though workplace homicides are down, financial stress could still lead to other acts of violence, acts that often go unreported, Schouten cautioned.

Nearly 2 million American workers report being victims of workplace violence annually, according to the Occupational Safety and Health Administration, which defines workplace violence as "any act or threat of physical violence, harassment, intimidation, or other threatening disruptive behavior that occurs at the worksite." It ranges from threats and verbal abuse to physical assaults and even homicide.

Losing a job, getting a demotion or having difficulty finding a new position could be triggers that — when coupled with other environmental and individual factors — send someone over the edge, Schouten said.

Carolyn Reinach Wolf, an attorney partner at Abrams & Fensterman on Long Island who specializes in violence prevention and identification, said employers and co-workers should be aware of red flags that could indicate a person poses a threat: erratic behavior; sudden isolative behavior; threats or negative statements about their lives and angry outbursts.

But she said that many times it is difficult to predict how stress and pressure affects individuals and what sets people off, as there is no standard profile of aggressors.

"Stress is stress, and people's limits are people's limits," she said. "It really comes down to coping and family background. Many of these are just spontaneous reactions."

Still, Schouten said most workplaces lack policies to handle violence. In 2005, about 70 percent had none, he said.

Schouten said workplaces should have teams trained to deal with threats and violent acts as well as enforced zero-tolerance policies stating that employers will immediately investigate these situations.

"That's a clear message to the work force," Schouten said.

He also said it helps when managers or supervisors have open-door policies, anonymous tip lines, health services and employee assistance programs. Managers and co-workers also should not be afraid to approach one another if they sense they're distressed.

Wolf said it also is important that employers, when laying off individuals, recognize the potential problem that could be caused.

"The lifestyle that people have led and are used to having — a house, a car, sending their kids to college — and then being laid off is a tremendous stress," Wolf said. "And that all needs to be taken into consideration when laying off."